This study is looking at two treatments for a type of lung cancer called metastatic non-small cell lung cancer (NSCLC). It compares a medicine called pembrolizumab (MK-3475) used alone versus in combination with another medicine, sacituzumab govitecan. The main goal is to see which treatment helps patients live longer without their cancer getting worse, which is called progression-free survival (PFS), and overall survival (OS). To be part of this study, you need to have a specific score called PD-L1 TPS (Tumor Proportion Score) of 50% or higher, which means that a certain protein is present on your cancer cells. This study does not accept people with certain other health conditions, like heart disease or active infections. If you decide to participate, you must not have received certain treatments before. The study will measure the effectiveness of the treatments by looking at changes in the cancer as per specific guidelines.

• The study involves two different treatment methods: one with two medicines and one with just one.
• Participants need to have a specific type of lung cancer and a certain score on their tumor cells.
• You can't join if you have certain health conditions or have had specific treatments before.